China — the country claiming the largest portion of the sea and also attracting the sharpest criticism — sent a low-ranking delegation to the conference. The snub was intended as a signal, said Ernie Bower, a Southeast Asia expert at the Center for Strategic and International Studies.

“Because the conference is so important to the Singaporeans, it’s basically China telling them, ‘You guys need to do more to control your ASEAN brethren — Philippines and Vietnam,’ ” Bower said. “There’s clear nervousness over how Philippines are playing their hand.”

The Obama administration’s overall Asia strategy was developed out of a belief that China responds best to a position of strength, when the United States has other countries working with it. According to senior U.S. officials, the policy reflects an intense study of historical hegemonic shake-ups: the rise of the United States as a global power; Germany’s rise in Europe after World War I; Athens and Sparta. The idea was to turn to history for answers as the United States confronts the next rising superpower: China.